Attachments
data class AttachmentsUpdated(val updatedAttachments: List<ZyncAttachment>, val deletedAttachmentUids: List<String>) : AttachmentChangeEvent, ChangeEvent<ZyncAttachment, String>
Event triggered when attachments are updated via delta sync. Contains a list of attachments that were found during background sync. Clients should decide whether each attachment is new or updated based on their local state.